HTML to PDF convert in Go using wkhtmltopdf using C library. Is it possible?

[Nikolaj Makhinko]

I've tried to connect wkhtmltopdf converter with Cgo, but after several hours it still doesn't work. Probably the cause is my low experience in C. But before I continue digging I would be happy to know if it is possible without pain. Also I would appreciate any advice on how to connect wkhtmltopdf C library with Go.

[azuma.4...@gmail.com]

+1

[yeer]

any progress? 

On Wednesday, March 19, 2014 4:21:34 PM UTC+8, Nikolaj Makhinko wrote:

[Nikolaj Makhinko]

Temporary I've solved it with exec:

cmd := exec.Command("xvfb-run", "wkhtmltopdf", "-", path)

cmd.Stdin = strings.NewReader(raw)

So the issue is still relevant.

[Mauro Risonho de Paula Assumpção]

+1

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[Kevin D]

In production, I call it externally the same way. I was going to check out the bindings, but I may be moving over to princexml and it has no bindings.

[Jsor]

Exactly what errors are you getting? I'm relatively experienced with Cgo so I may be able to help even if I'm not really familiar with the library.

[Nikolaj Makhinko]

I've included the pdf.h into the go without errors.  I've tried to reproduce the following example https://github.com/clowder/wkhtmltopdf/blob/master/examples/pdf_c_api.c

Just using "C." prefix isn't working. 

[bigras...@gmail.com]

I reproduced most of the pdf_c_api.c example (I didn't have time to do the callbacks).

And by the way, I think we don't need xvfb-run anymore if we use the static version. See https://code.google.com/p/wkhtmltopdf/issues/detail?id=3

package main

import (

"fmt"

)

//#cgo CFLAGS: -IC:/wkhtmltopdf/include

//#cgo LDFLAGS: -lwkhtmltox -LC:/wkhtmltopdf/lib

// #include <wkhtmltox/pdf.h>

import "C"

func main() {

C.wkhtmltopdf_init(0)

gs := C.wkhtmltopdf_create_global_settings()

globalSettings := [][2]string{

{"out", "out.pdf"},

{"size.paperSize", "letter"},

}

for _, setting := range globalSettings {

C.wkhtmltopdf_set_global_setting(gs, C.CString(setting[0]), C.CString(setting[1]))

}

os := C.wkhtmltopdf_create_object_settings()

objectSettings := [][2]string{

{"page", "http://wkhtmltopdf.org/libwkhtmltox/"},

{"footer.center", "[page] / [toPage]"},

}

for _, setting := range objectSettings {

C.wkhtmltopdf_set_object_setting(os, C.CString(setting[0]), C.CString(setting[1]))

}

c := C.wkhtmltopdf_create_converter(gs)

C.wkhtmltopdf_add_object(c, os, nil)

if C.wkhtmltopdf_convert(c) != 1 {

fmt.Println("http error code", C.wkhtmltopdf_http_error_code(c))

}

C.wkhtmltopdf_destroy_converter(c)

C.wkhtmltopdf_deinit()

[Nikolaj Makhinko]

Thank you. Looks promising. I'm trying to reproduce it in Linux environment(Ubuntu and CentOS) but I'm getting an error:

/usr/bin/ld: cannot find -llibwkhtmltox

collect2: ld returned 1 exit status

The lib name was changed according to the Linux installation(x86_64).

/home/go/app/wkhtmltox/lib folder contains following files:

libwkhtmltox.so.0

libwkhtmltox.so.0.12

libwkhtmltox.so.0.12.0

The header looks like:

//#cgo CFLAGS: -I/home/go/app/wkhtmltox/include

//#cgo LDFLAGS: -llibwkhtmltox -L/home/go/app/wkhtmltox/lib

//#include <wkhtmltox/pdf.h>

[Bruno Bigras]

Could you try :

//#cgo LDFLAGS: -lwkhtmltox -L/home/go/app/wkhtmltox/lib

[Nikolaj Makhinko]

Yes, I tried it. But it doesn't work. 

I've played a little bit with linking and have it working with the following header:

//#cgo CFLAGS: -Iwkhtmltox/include

//#cgo LDFLAGS: -Wl,-rpath, wkhtmltox/lib/libwkhtmltox.so

//#include <wkhtmltox/pdf.h>

import "C"

libwkhtmltox.so was created as symlink to  libwkhtmltox.so.0

Also the following files were copied to /usr/lib folder:

libwkhtmltox.so  

libwkhtmltox.so.0  

libwkhtmltox.so.0.12  

libwkhtmltox.so.0.12.0

Now the question is: how to get rid of the files copying to /usr/lib?

[markg...@gmail.com]

Sorry to make a call back to this but were you able to statically link the wkhtmltox library to your golang app?

I run go build --ldflags '-extldflags "-static"' main.go with the following start of main.go:

//#cgo CFLAGS: -I/usr/local/include/wkhtmltox                                                                                                                                                     

//#cgo LDFLAGS: -Wl,-rpath, /usr/local/lib/libwkhtmltox.so                                                                                                                                        

//#include <pdf.h> 

And receive:

# command-line-arguments

/usr/bin/ld: attempted static link of dynamic object `/usr/local/lib/libwkhtmltox.so'

collect2: error: ld returned 1 exit status

/home/mark/.gvm/gos/go1.4/pkg/tool/linux_amd64/6l: running gcc failed: unsuccessful exit status 0x100

Apologies if the answer is obvious. I'm just unfamiliar with the gcc and linking go and C.

[Ian Lance Taylor]

On Fri, May 29, 2015 at 10:30 AM, <markg...@gmail.com> wrote:
>
> Sorry to make a call back to this but were you able to statically link the
> wkhtmltox library to your golang app?
>
> I run go build --ldflags '-extldflags "-static"' main.go with the following
> start of main.go:
> //#cgo CFLAGS: -I/usr/local/include/wkhtmltox
> //#cgo LDFLAGS: -Wl,-rpath, /usr/local/lib/libwkhtmltox.so
> //#include <pdf.h>
>
> And receive:
> # command-line-arguments
> /usr/bin/ld: attempted static link of dynamic object
> `/usr/local/lib/libwkhtmltox.so'
> collect2: error: ld returned 1 exit status
> /home/mark/.gvm/gos/go1.4/pkg/tool/linux_amd64/6l: running gcc failed:
> unsuccessful exit status 0x100
>
> Apologies if the answer is obvious. I'm just unfamiliar with the gcc and
> linking go and C.

You can not statically link a .so file. You need a .a file. If you
are installing from a package manager such as apt-get or yum, the .a
file is typically packaged separately in a -devel package.

Ian